The project seeks to examine the behavioral and neural development of animals reared with a sensory substitution device. Five groups of four stumptail macaques will be raised from birth to three months, and one group to 6 months. The experimental groups will be raised without vision but with the Trisensor Aid (TSA) in continuous use, one group to 3 months and one to 6 months. One control group will be reared without vision but with a silent, dummy version of the device, another with a sound-making but non-functional device and a fourth group with a sensor but with normal vision. Finally, four normal, colony-reared animals will be studied. The TSA is an advanced experimental version of a blind travel aid, the Sonicguide. The research will explore the advantages that the TSA provides for infant monkeys in early development. Behavioral observations and tests will be made throughout the three- or six-month period, including cage observation, and tests of auditory attention as shown by reaching to sounds, silent objects and looming stimuli, as well as of mobility and locomotor behavior in a novel environment. At the end of the rearing period, the animals will be sacrificed and neuroanatomical studies done of visual, auditory and motor areas in the cortex. The research is significant in addressing questions that are important to visually-impaired human infants but which are difficult to perform with humans. Thus the neuroanatomical study could not be performed on humans, even though the possibility of cortical changes after prolonged early use of a prosthesis could have considerable importance. Even behavioral studies with infants have been difficult to conduct because of the problems of obtaining and working with blind infants. The TSA is a potentially important tool for research as well, as it allows novel questions of intermodal organization to be studied, via the sensory substitution paradigm. Finally, the correlation of behavioral and neuroanatomical evidence is important in drawing and integrated picture of neocortical and behavioral development.